The present invention relates to flaw detection, and more particularly, to a novel surface flaw detection system utilizing video sensing and processing apparatus.
The manufacture of many objects requires detection of flaws on the object's surface, particularly by apparatus which does not contact the object to be tested, to prevent damage to the object. Illustratively, in the construction of a high voltage cable, successive layers of extruded plastic insulation are fabricated over a conductive core; it is necessary to detect voids and other surface flaws, such as indentations, scrapes, pits and the like, on the insulation layer surface, to prevent possible corona effects and breakdown failure of the cable between the conductive core and an exterior-wound conductive jacket. Traditionally, inspection of the surface of the cable insulation was performed, prior to exterior conductive layer fabrication, by visual or tactile inspection. Detection of minute flaws is highly improbable, especially if the object is moving at any appreciable velocity past the observer. An automatic system for detecting surface flaws, with high probability of generating an alarm for flaws exceeding a preselected set of characteristics, is highly desirable.